1. Field of the Invention
The present invention relates to measurement apparatus, and more particularly to apparatus for measuring the damping performance of shock absorbers directly on a vehicle.
2. Descripton of the Prior Art:
The mechanics of damping of a automobile shock absorber are typically complex being designed to accommodate a wide range of suspension activity and any manual methods of testing of the nonlinear behavior thereof is highly subjective and often produces erroneous conclusions. Thus the effectiveness of automobile shock absorbers is typically hard to ascertain either by visual inspection or manual testing and numerous mechanical test procedures have been proposed in the past for measuring the damping performance thereof. Heretofore such testing procedures almost always required the removal of the shock absorber from the vehicle in which it is installed since only in such separated condition could the damping performance of the shock absorbers be accurately measured. Furthermore, the shock absorbers on the vehicle function in close association with various other suspension elements which in themselves are often non-linear, thus any measurement of the shock absorber performance must necessarily decouple or compensate for the various contributions to the dynamics of motion of the compound spring structure of the suspension. Such shock absorbers are typically included as part of the automative equipment covered by the general sellers' warranty and since many idiosyncratic opinions are possible as to the quality of the ride at any level of suspension activity a positive method of identifying the functioning of the shock absorber has been quite bothersome in the past. It is also generally recognized that faulty shock absorbers can seriously degrade the handling characteristics of a vehicle and therefore influence the safety of operation. A positive and convenient means for identifying such faulty shock absorbers in vehicle safety inspections is therefore greatly needed at present.
Heretofore most prior art devices would produce a convincing reading of shock absorber effectiveness only after a considerable amount of labor had been expended, i.e. only after the shock absorber had been removed from the car and tested by conventional testing devices. This particular problem has presented significant labor costs in the post-sale services and therefore is a substantial cost item for the automobile manufacture. Other heretofore proposed apparatus which provides a direct reading of shoch absorber quality is typically complex, requiring large amounts of external power to excite the automobile, and is therefore expensive to produce and operate.